Dynamic address mapping of a fibre channel loop ID

ABSTRACT

The present invention is a method and a system for dynamic mapping of a fiber channel loop ID in an ALPA loop. Based on reserved address information for the fiber channel system and a number of select ID bits for a slot ID, a dynamic drive mapping table is created. A unique address may be assigned to each drive and each controller in the ALPA loop. The created drive mapping table may be stored on logic decoding circuitry of an adaptor card coupled to each disk drive in the ALPA loop. When fiber channel loop ID signals are sent from a backplane, the fiber channel loop ID signals are translated into seven bits within an ALPA address range based on the dynamic drive mapping table. The converted signals may be sent to the disk drive coupled the adaptor card at boot up time.

FIELD OF THE INVENTION

The present invention generally relates to the field of computernetworking systems, and particularly to a method and system of dynamicmapping of a fibre channel loop ID in an Arbitrated Loop Port Address(ALPA) space.

BACKGROUND OF THE INVENTION

The Fibre Channel (FC) protocol communication standard has beendeveloped to provide practical, inexpensive, and expandable means oftransferring data between workstations, mainframes, storage devices andother peripheral devices. Fibre Channel supports different topologies,including a point-to-point topology, an arbitrated loop topology and afabric attached topology. The arbitrated loop topology attaches devicesin a loop, creating a Fibre Channel Arbitrated Loop (FC-AL). The FibreChannel Arbitrated Loop (FC-AL) requires a unique address for eachdevice in the loop. The unique address is called an Arbitrated LoopPhysical Address (ALPA).

A single FC-AL typically supports up to 127 devices and one connectionto a fabric switch may exist in a single ALPA space. Data within an ALPAspace physically travels from node to node in a daisy-chain fashion,ultimately traveling in a loop. Control by a device on the loop isobtained through the process of loop arbitration, after which the devicewinning arbitration sends data.

In a particular FC storage system having FC-ALs, the FC storage systemmay communicate with several shelves. Each shelf contains several diskdrives, associated control hardware, and several backplanes. Typically,legal ALPAs per a FC-AL are not sequential from 0 to 126. However, it isdesirable for other parts of the FC storage system to useeasy-to-understand sequential numbers for ALPA. Consequently, “selectID” (sequential from 0 to 126) may be used in the FC storage system andthe Select ID may be mapped to a proper ALPA through various methods.

Some FC storage systems may allow plugging a disk drive into abackplane. If a disk drive is removed from the backplane and pluggedinto a different location in the backplane, the FC storage system mayuse the label information recorded on the drive to recognize where thisdrive should be mapped into its file management tables. It is importantto maintain such flexibility in data security applications or forconfiguration expansion. Thus, some FC storage systems are physicallocation dependent systems to achieve such flexibility, having aphysical address for each drive to remain consistent.

A Select ID signal may be used in FC storage systems to assign aphysical location for each connection to a backplane, allowing themanagement of configuration and the simple identification of devicesthat need to be changed for maintenance reasons. Additionally, theSelect ID signal may be able to specify a physical address for eachdrive. In the particular FC storage system, the Select ID signal may bea seven-bit signal sent from the backplane since a 7-bit binary numberis suitable for representing the decimal numbers from 0 to 126. TheSelect ID signal may be used to create the binary value of the Select IDto the drive in that location.

The Select ID is mapped to the proper ALPA for a drive. The 7-bit SelectID may have two main fields: “shelf ID” which is a shelf-within-the-loopportion and “slot ID” which is a drive-slot-within-the-shelf portion.The “shelf ID” and the “slot ID” may be used to assign ALPA addressesfor keeping the software simple. For example, 4 bits of the Select IDmay be used for the Slot ID bits to encode up to 16 drive slots pershelf. Each drive slot may have a constant “slot ID” assigned to it bythe hardware (fixed constant defined by the backplane wiring in theshelf). The remaining 3 bits of the Select ID may be used for the “shelfID” bits. The “shelf ID” bits are determined by a user-settable switch,so the user can combine identical shelves into a single loop and thenset the “shelf IDs” to unique numbers, thus making sure the Select IDfor each drive is completely unique in the FC-AL loop.

The backplane may use SEL_(—)6 through SEL_(—)0 ID lines to send aSelect ID signal. FC storage systems may assign the lower bits of theSelect ID signal (i.e. Slot ID bits) by hardwiring them LOW or HIGH ateach drive slot on the backplane in order to keep hardware simple. Theupper bits of Select ID signal (i.e. Shelf ID bits) are typically set tobe the same across all drive slots in a shelf. Thus, shelves tend tocontain a number of drives that are a power of 2 or slightly less inorder not to waste available ALPA addresses.

As a result, a conventional FC storage subsystem includes a shelfcontaining 16 disk drives, 32 disk drives, and the like. A designer maydesire various numbers of disk drives per shelf, for example, 22 diskdrives per shelf. In such a case, three shelves per a FC-AL may beallowed in order to preserve reserved addresses and 30 addresses may bewasted, compared to a storage subsystem having 32 disk drives per shelf.If four shelves are allowed, it is difficult to fit the address spaceinto available ALPA addresses without reuse of reserved addresses forthe FC storage subsystem. Examples of the reserved addresses includereserved addresses for a host bus adapter (HBA), electronics for SCSIEnclosure Services (SES controller), and the like. A typical FC storagesystem may need at least one host bus adapter (HBA) and an SEScontroller per shelf. In the FC storage system, the highest Select ID126 may be reserved for a HBA and one Select ID may be assigned to eachSES controller in the shelves.

Further, a designer may desire a non-fixed number of disk drives pershelf, for example, 16 disk drives per shelf now and then 22 disk drivesper shelf later. In such cases, it is unavoidable to implement a complexmethod of ALPA address mapping through some decoding logic in thebackplane or elsewhere in the drive enclosure. Typically, a card thatplugs into the backplane may be used to implement a complex method ofALPA address mapping. However, this approach may require more signalslines between the backplane (the decoding logic circuit) and the driveslots, resulting in higher pin counts of the card. It is very costly andcomplex.

Additionally, under the FC standard, all Select IDs need to be unique ina given FC-AL. Conventional FC storage systems assign a unique Select IDto each device (e.g. each pluggable disk drive and the like). One of theconventional FC storage subsystems may include 14-16 drives per shelf.In such a system, 4 bits of the Select ID may be used for the slot IDbits to encode up to 16 drive slots per shelf. Each drive slot may havea constant “slot ID” assigned to it by the hardware (fixed constantdefined by the backplane wiring in the shelf). The remaining 3 bits ofthe Select ID may be used for the “shelf ID” bits. The “shelf ID” bitsare determined by a user-settable switch, so the user can combineidentical shelves into a single loop and then set the “shelf IDs” tounique numbers, thus making sure the Select ID for each drive iscompletely unique in the FC-AL loop. For example, a 14-drive shelf with“shelf ID” set to 0 would have drives numbered with Select IDs from 0 to13 (the offset of 0 for shelf 0, plus 0 to 13 for the drive slot). Shelf1 would have drives numbered with Select IDs from 16 to 29 (the offsetof 16 for shelf 1, plus 0 to 13 for the drive slot). Shelf 2 would havedrives numbered from 32 to 45 (the offset of 32 for shelf 2, plus 0 to13). Other devices in the FC-AL loop may have assigned reservedaddresses. Examples of the reserved addresses include reserved addressesfor a host bus adapter (HBA), electronics for SCSI Enclosure Services(SES controller), and the like. A typical FC storage system may need atleast one host bus adapter (HBA) and an SES controller per shelf.

In the FC storage system, the highest Select ID 126 may be reserved fora HBA. In order not to reuse reserved addresses, the block of Select IDsbased on the last “shelf ID” may be reserved. In other words, the entireSelect IDs in the range of the last “shelf ID” may be reserved and notto be used by disk drives. As described above, a FC storage systemincluding 16-drive shelves typically uses 3 bits of the Select ID forthe “shelf ID”. Thus, eight “shelf IDs” may be available per FC-AL.Since the highest “shelf ID” (or a block of 16 Select IDs) may bereserved, seven “shelf IDs” may be available for shelves per FC-AL.Consequently, the FC storage system may be allowed to include 7 shelvesand 7*16=112 total disk drives per FC-AL. Each SES controller in theshelf may need one Select ID. The FC storage system may be able to use112 (for disk drives)+7 (for SES controllers)=119 total Select IDswithout reusing the reserved block of Select ID.

However, a certain FC storage system may include a larger size shelf,such as a 32-disk shelf, and the like. In such a system, the 7-bitSelect ID may be split into 5 bits of “slot ID” (32 slots) and 2 bits of“shelf ID” (up to 4 shelves). The highest “shelf ID” may be reserved fora HBA and, as a result, a block of 32 Select IDs associated with thehighest “shelf ID” may be reserved and not supposed to be used by diskdrives. The FC storage system may be allowed to have three shelves and3*32=96 total disk drives per FC-AL. In this manner, the reserved blockof 32 Select IDs may not be reused. However, a significant chunk ofSelect IDs is wasted. As such, when the FC storage system includesshelves with the number of disk drives being a power of 2, such as 16,32, 64 and the like, the larger the shelf is (the more disk drives pershelf), the more Select IDs (i.e more ALPA addresses) the FC storagesystem wastes due to the size of the reserved block of Select IDs.

Therefore, it would be desirable to provide a method and system formapping the Select ID signal in available ALPA addresses without wastinga significant chunk of available ALPA addresses for a FC storagesubsystem having non-fixed numbers of disk drives per each shelf. Itwould be also desirable to provide such a method and system for mappingthe select ID signal in available ALPA addresses through use of a smallnumber of signal lines. It would also be desirable to provide a methodand system for assigning a unique Select ID to a FC storage device so asto maintain desirable numbers of disk drives in a given FC-AL whilepreserving reserved Select IDs and providing a method and system formaximizing use of resources in the FC-AL.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a method and a system fordynamic mapping of a fibre channel loop ID in ALPA addresses for astorage subsystem having various numbers of disk drives for each shelf.The present invention may create a dynamic drive mapping table forchanges in the storage system and thus required minimal changes on backpanel hardwires connected to a switch selecting a shelf ID (a shelf IDselect switch).

In an aspect of the present invention, a method for dynamic mapping of afibre channel select ID for a storage subsystem is provided. The methodmay retrieve reserved address information for the storage subsystem. Anumber of select ID bits which are utilized for a slot ID of adesignated disk drive on each shelf may be determined. The method maydetermine whether a dynamic drive mapping table is necessary. If thedynamic drive mapping table is necessary, the dynamic drive mappingtable may be created based on the reserved address information and thenumber of select ID bits for the slot ID. A unique address may beassigned to each drive and each controller in the ALPA loop. The createddynamic drive mapping table may be stored on logic decoding circuitry ofan adaptor card coupled to each disk drive.

In an additional aspect of the present invention, when fibre channelloop ID signals are sent from a backplane to an adaptor card coupled toa designated disk drive, the fibre channel loop ID signals may betranslated into seven bits within an ALPA address range based on thedynamic drive mapping table. The converted signals may be sent to thedesignated disk drive. In this manner, the backplane may have minimalhardwires coupled to a shelf ID select switch, having few Select IDlines connected to all disk drives.

In a further aspect of the present invention, a storage subsystem fordynamic mapping of a fibre channel loop ID (a select ID) in ALPAaddresses may be provided. The storage subsystem may include severalFC-ALs each of which has an exclusive address space. The storagesubsystem may include several backplanes for receiving a slot ID and ashelf ID and shelves coupled to its associated backplane. The backplanesmay be connected via a FC-AL. Depending on the storage subsystemarchitecture; each shelf may include various numbers of disk driveswhich are coupled to adaptor cards. Each adaptor card may store adynamic drive mapping table. Each backplane is capable of sending afibre channel loop ID to an adaptor card coupled to a designated diskdrive. When the adaptor card receives the fibre channel loop ID, it maytranslate the fibre channel loop ID to a different loop ID based on thedynamic drive mapping table which may be sent to the designated diskdrive.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention as claimed. The accompanyingdrawings, which are incorporated in and constitute a part of thespecification, illustrate an embodiment of the invention and togetherwith the general description, serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The numerous advantages of the present invention may be betterunderstood by those skilled in the art by reference to the accompanyingfigures in which:

FIG. 1 illustrates a schematic block diagram of storage systems coupledto a host server in accordance with an exemplary embodiment of thepresent invention;

FIG. 2 illustrates a block diagram of an internal board layout fordynamic mapping of a FC loop ID for the storage system shown in FIG. 1;

FIG. 3 is a flow diagram of a method for creating a dynamic drivemapping table in accordance with an exemplary embodiment of the presentinvention; and

FIG. 4 is a flow diagram of a method implemented in accordance with anexemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the presently preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

The present invention is directed to a method and a system for dynamicmapping of a fibre channel loop ID in ALPA addresses for a storagesystem having various numbers of disk drives for each shelf. The presentinvention may create a dynamic drive mapping table for changes in anumber of disk drives of the storage system and thus allow a backplaneto have minimal hardwires coupled to a switch for selecting shelf ID.Consequently, the present invention may provide a cost effectivesolution for the storage system having various numbers of disk drivesfor each shelf.

In the following description, numerous specific descriptions are setforth in order to provide a thorough understanding of the presentinvention. It should be appreciated by those skilled in the art that thepresent invention may be practiced without some or all of these specificdetails. In some instances, well known process operations have not beendescribed in detail to prevent obscuring the present invention.

Referring now to FIG. 1, a schematic block diagram 100 of exemplarystorage subsystem including multiple shelves is depicted. Multipleshelves 102-108 may have fibre channel connectivity to a host server110. In an embodiment of the present invention, the multiple shelves102-108 may have fibre channel connectivity to a filer head (not shown).For example, a particular FC storage system may comprise, but notlimited to, a hardware platform which includes a filer head containingCPU, memory, RAM, and the like. The file head may be communicativelycoupled to a storage subsystem having multiple shelves containingseveral disk drives and associated control hardware. The multipleshelves may be connected to the filer head with several Fibre ChannelArbitrated Loops (FC-ALs), each of which has an exclusive address space.It is to be noted that the desirable number of disk drives and shelvesfor a particular storage system may be inherently limited by thelimitation of an ALPA space. For example, in a particular embodiment,each shelf in the storage system may contain 24 disk drives (such as ATAhard drives and the like). When seven select ID signals from backplaneare converted into ALPA addresses, 126 addresses are available perFC-AL. In the particular embodiment, several addresses may be reservedto meet the Fibre channel standard requirement by ANSI X3T11 task groupto define a serial I/O channel for interconnecting a number ofheterogeneous peripheral devices to computer systems as well asinterconnecting the computer systems themselves through optical fiberand copper media at gigabit speeds. For example, lower eight addresses(address 0-7) may be reserved for Small Computer System Interface (SCSI)initiators and the highest (address 126) for a Fibre Channel switch. TheSCSI initiators are devices in the serial I/O channel issuing commands.In such case, 118 addresses may be available for the shelves. In theparticular embodiment, each shelf may use 24 addresses for disk drivesand 2 addresses for controllers. Each of the FC-ALs may be capable ofsupporting up to four shelves.

Each shelf may also include a Controller Module (such as Serial-ATAController Module (SCM), or the like). For example, the SCM may beutilized to bridge from FC (Fibre Channel) to Serial-ATA (S-ATA). The FCloop may connect the SCM on the rear of the shelf. The Controller Modulemay be connected into the rear side of the backplane. In the particularembodiment, the front side of the backplane provides 24 individualconnections for each disk drive. An adapter card may be communicativelycoupled to each disk drive to complete an address mapping.

Referring now to FIG. 2, a schematic block diagram of an exemplary shelf200 is depicted. The shelf 200 may include several disk drives 210, 212and a backplane 206. The backplane 206 may provide multiple individualconnections of each disk drive 210. Each disk drive 210 may be coupledto an adaptor card 208 which may translate control signals. The adaptorcard 208 may be a circuit board (panel board) configured to decodecontrol signals.

The backplane 206 may receive shelf ID signals from a shelf ID selectswitch 202 (such as a Thumbwheel switch which is a manually operableshelf ID select switch, or the like). A FC Loop/Switch circuit 204 maysend slot ID signals to the backplane 206. The backplane may combine theshelf ID signals and the slot ID signals to generate a FC loop ID (e.g.select ID, or the like) signal. The FC loop ID (select ID) signal may besent from the backplane 206 to the adaptor card 208 coupled to adesignated disk drive.

For example, the backplane 206 may receive Sel_(—)5 and Sel_(—)6 signalsfrom a shelf ID select switch 202. In one embodiment of the invention, aFC Loop/Switch circuit 204 may send five bit signals including Sel_(—)0,Sel_(—)1, Sel_(—)2, Sel_(—)3, and Sel_(—)4 to indicate which drive sloton the backplane 206 will be designated. Consequently, a select IDsignal including seven SEL_x bits may be sent from the backplane 206 tothe adaptor card 208.

In a particular embodiment, the storage system may include 24 diskdrives for each shelf. In such a case, four shelves including 24 diskdrives may be allowed to be connected in a FC loop since ALPA supports126 addresses. Typically, the storage system may reserve few addressesfor initiators and switch ports. For instance, the first lower 8addresses are reserved for the initiators and the highest ID (126) isreserved for switch ports. The lower 5 bits of a select ID may bereserved for a slot ID and the upper 2 bits a select ID may be used fora shelf ID.

In order to reserve addresses for initiators and switch ports withoutcreating complicated hardwires connected to the shelf ID select switchon the backplane, a dynamic drive mapping table may be created totranslate a select ID signal to an address within available ALPAaddresses (e.g. from 8 to 125 in the particular embodiment). In apreferred embodiment, the dynamic drive mapping table may be stored inlogic decoding circuitry on each adaptor card in the storage system. Thelogic decoding circuitry may a combination of several programmable logicgates. In an embodiment of the present invention, the dynamic drivemapping table may be reprogrammable within the logic decoding circuitrywhenever a new dynamic drive mapping table is required. The lower 5select ID bits may be hardwired from 0 to 23 on the backplane 106. Theupper two bits may come from the thumbwheel switch (the shelf ID selectswitch) 102 with two bits giving 0, 1, 2, or 3.

In an embodiment of the present invention, two Select ID lines from theshelf ID select switch is suitable for being bused to all drives in ashelf when the dynamic drive mapping table translates the select IDsignal to an address within available ALPA addresses. In the embodiment,the backplane may utilize two hardwires from the shelf ID select switchfor the FC loop ID mapping. As such, the backplane may be designed tohave minimal hardwire connected to the shelf ID select switch.

An exemplary dynamic drive mapping table for the particular embodimentmay be created as shown below:

Drive 0: Drive 23: Shelf ID SEL_4,3, SEL _4,3, Controller ControllerSEL_6 SEL_5 2,1,0) . . . 2,1,0) A B 0x0b 0x0b 16 39 40 41 0x0b 1x0b 4467 68 69 0x1b 0x0b 72 95 94 97 0x1b 0x1b 100 123 124 125

It is to be noted that the above exemplary dynamic drive mapping tableis described for illustrative purposes. Those of ordinary skill in theart will appreciate that there are various ways to create a dynamicdrive mapping table suitable for the storage subsystem having FC-ALconnectivity in accordance with the present invention.

In one embodiment, a designated adaptor card would receive the sevenSEL_x (e.g. SEL_(—)0, SEL_(—)1, SEL_(—)2, SEL_(—)3, SEL_(—)4, SEL_(—)5,and SEL_(—)6) signals from the backplane and convert them to a differentloop ID of seven bits according to the dynamic drive mapping table andsend them to a disk drive coupled to the designated adaptor card at bootup time.

Referring now to FIG. 3, a flow diagram 300 of a method for creating anew dynamic drive mapping table is depicted. In step 302, reservedaddress information for the storage system may be retrieved. Typically,the FC storage system may reserve several ALPA addresses in order toconform to the FC standard (ANSI X3T11). For instance, first lower 8addresses (ALPA address 0, 1, 2, 3, 4, 5, 6, and 7) are reserved for theSCSI initiators and the highest ID (ALPA address 126) is reserved forthe fibre switch port. The reserved address information may be stored inmemory of an adaptor card. Alternatively, the reserved addressinformation may be stored in non-volatile memory, flash memory or thelike in the file header of the storage system. The reserved addressinformation may be provided from a user through a recoding medium (e.g.floppy disk, CD ROM, DVD ROM, or the like), a keyboard input, or thelike to the host server coupled to the storage subsystem.

A number of select ID bits to represent a slot ID may be determinedbased on a number of disk drives on a shelf. For example, if each shelfincludes 14 disk drives, 4 select ID bits are required for a slot IDwhile 5 select ID bits are required for a slot ID if each shelf includes24 disk drives. As such, the method may determine whether a dynamicdrive mapping table is to be created for the storage system in step 304.The dynamic drive mapping table is required when the select ID bits fora slot ID indicates that an overlapped use of the reserved addresses(i.e. reuse of the reserved address by disk drives) may be present inthe FC-AL. Accordingly, the dynamic drive mapping table for the storagesystem will be created based on the reserved address information and thenumber of select ID bits in step 306. A unique address within availableALPA addresses may be assigned to each drive and each controller in theALPA loop. Thus, the dynamic drive mapping table may ensure that thereis no overlapping use of reserved addresses. As describe above, reservedaddresses may be used for SCSI initiators, a fibre switch port, and thelike. The created dynamic drive mapping table may be stored on the logicdecoding circuitry of each adaptor card coupled to a disk drive in theALPA loop 308.

In a particular embodiment, the method may be implemented by the FCstorage system having the NETAPP® DATA ONTAP™ operating system installedon a hardware platform that includes a filer header and communicativelycoupled to the storage subsystem including several shelves in FC-ALs.

Referring now to FIG. 4, a flow diagram 400 of a method implemented inaccordance with the present invention is depicted. The method may startwith a step receiving seven SEL_x (e.g. SEL_(—)0, SEL_(—)1, SEL_(—)2,SEL_(—)3, SEL_(—)4, SEL_(—)5, and SEL_(—)6) signals from the backplane402. When the select ID signals are sent from a backplane to adesignated adaptor card, the select ID signals are translated into sevenbits within an ALPA address range based on the dynamic drive mappingtable. The method may consult the dynamic drive mapping table stored onthe logic decoding circuitry of the designated adaptor card 404. Thereceived seven SEL_x signals may be translated into seven bits within anALPA address range based on the dynamic drive mapping table 406. Theconverted signals may be sent to a disk drive coupled to the designatedadaptor card at boot up time.

In an embodiment, the ALPA address for the devices attached to thefabric port on the shelf may be predetermined by the dynamic drivemapping table in order to simplify fabric routing. The ALPA values maybe contiguous among drives in each shelf. The strategy is to allocatenumerically similar ALPA ranges to fabric ports to simplify routing.Advantageously, the present invention allows various numbers of shelveswith various numbers of drives to be attached in an ALPA loop withoutinterfering with reserved addresses. Additionally, the present inventionmay utilize two Select ID lines bused to all drives so that thebackplane does not need additional hardwires connected to the shelf IDselect switch for the FC loop ID mapping. Accordingly, the presentinvention may provide a cost effective solution for the storage systemsince each backplane may be designed to have minimal hardwire connectedto the shelf ID select switch. In an alternative embodiment of thepresent invention, a controller card may be utilized to send the uppertwo bits to every drive.

In the exemplary embodiments, the methods disclosed may be implementedas sets of instructions or software readable by conventional generalpurpose digital computers. Further, it is understood that the specificorder or hierarchy of steps in the methods disclosed are examples ofexemplary approaches. Based upon design preferences, it is understoodthat the specific order or hierarchy of steps in the method can berearranged while remaining within the scope and spirit of the presentinvention. The accompanying method claims present elements of thevarious steps in a sample order, and are not necessarily meant to belimited to the specific order or hierarchy presented.

It is to be understood that the present invention may be convenientlyimplemented in forms of a software package. Such a software package maybe a computer program product which employs a computer-readable storagemedium including stored computer code which is used to program acomputer to perform the disclosed function and process of the presentinvention. The computer-readable medium may include, but is not limitedto, any type of conventional floppy disk, optical disk, CD-ROM,magneto-optical disk, ROM, RAM, EPROM, EEPROM, magnetic or optical card,or any other suitable media for storing electronic instructions.

1. A method for dynamic mapping of a fibre channel select identifier(ID) in Arbitrated Loop Port Address space for a storage subsystemincluding a plurality of disk drives, comprising: retrieving reservedaddress information; determining a number of select ID bits for a slotID; determining whether a dynamic drive mapping table is required toavoid an overlapped use of reserved addresses; creating the dynamicdrive mapping table based on the reserved address information and thenumber of select ID bits for a slot ID when the overlapped use of aplurality of reserved addresses is present; and storing the createddynamic drive mapping table on logic decoding circuitry of each adaptorcard of a plurality of adaptor cards, each disk drive of the pluralityof disk drives coupled to a separate adaptor card of the plurality ofadaptor cards, wherein the select ID signals are sent from a backplaneto each adaptor card coupled to a designated disk drive.
 2. The methodas described in claim 1, wherein the dynamic drive mapping table isreprogrammable to be stored on the logic decoding circuitry.
 3. Themethod as described in claim 1, further comprising: converting theselect ID signals sent from the backplane into seven bits within anArbitrated Loop Port Address range, based on the dynamic drive mappingtable.
 4. The method as described in claim 1, creating the dynamic drivemapping table step further comprising: assigning a unique address foreach drive; and assigning a unique address for each controller.
 5. Themethod as described in claim 4, wherein the unique addresses for eachdrive and each controller are not overlapped with the reservedaddresses.
 6. The method as described in claim 5, wherein the reservedaddresses are included in the reserve addresses information.
 7. Themethod as described in claim 3, further comprising: sending theconverted signals to the designated disk drive.
 8. The method asdescribed in claim 1, wherein the select ID signals include seven bits.9. The method as described in claim 2, wherein the dynamic drive mappingtable is reprogrammed if there is a change in a number of disk drivesincluded in each shelf.
 10. A system for dynamic mapping of a fibrechannel select identifier (ID) in Arbitrated Loop Port Addresses for astorage subsystem including a plurality of Fibre Channel ArbitrationLoops, the system comprising: means for retrieving information ofreserved addresses; means for determining a number of select ID bits forbeing utilized to select a designated fibre channel drive; means forcreating the dynamic drive mapping table based on the reserved addressinformation and the number of select ID bits and saving the dynamicdrive mapping table on logic decoding circuitry of each adaptor card ofa plurality of adaptor cards, each disk drive coupled to a separateadaptor card of the plurality of adaptor cards, when the number ofselect ID bits indicates that an overlapped use of the reservedaddresses is present in at least one of the plurality of Fibre ChannelArbitration Loops; and means for sending the select ID signals from abackplane to each adaptor card coupled to a designated disk drive,wherein each of the plurality of Fibre Channel Arbitration Loops has anexclusive address space.
 11. The system as described in claim 10,further comprising: means for converting the received select ID signalsfrom the backplane into seven bits based on the dynamic drive mappingtable, wherein the converted seven bits are within an availableArbitrated Loop Port Address range.
 12. The system as described in claim10, the creating the dynamic drive mapping table step means furthercomprising: means for assigning a unique address for each disk drive andeach controller in the storage subsystem.
 13. The system as described inclaim 12, wherein the unique address is not overlapped with reservedaddresses.
 14. The system as described in claim 11, further comprising:sending the converted signals to the designated disk drive from theadaptor card.
 15. The system as described in claim 10, wherein theselect ID signals include slot ID signals and shelf ID signals.
 16. Astorage subsystem capable of dynamic mapping of a fibre channel loopidentifier (ID) wherein the storage subsystem has a plurality ofreserved addresses, the storage subsystem comprising: a plurality ofbackplanes for receiving a slot ID and a shelf ID; a plurality ofshelves coupled to the plurality of backplanes, each of the plurality ofshelves including a plurality of disk drives, each individual disk drivebeing coupled to a separate adapter card of a plurality of adaptorcards, each of the plurality of adaptor cards including logic decodingcircuitry for storing a dynamic drive mapping table; a fibre channelloop switch control coupled to the plurality of backplanes, the fibrechannel loop switch control for sending signals for the slot ID to theplurality of backplanes; and a shelf ID select switch coupled to theplurality of backplanes, the shelf ID select switch for sending theshelf ID signals to the plurality of backplanes, wherein each of theplurality of backplanes is capable of sending a fibre channel loop ID toa designated adaptor card and the fibre channel loop ID includes thereceived slot ID and shelf ID.
 17. The storage subsystem as described inclaim 16, wherein the designated adaptor card converts the receivedfibre channel loop ID to a different loop ID based on the dynamic drivemapping table.
 18. The storage subsystem as described in claim 16,wherein the dynamic drive mapping table is created to avoid anoverlapped use of the plurality of reserved addresses.
 19. The storagesubsystem as described in claim 17, wherein the different loop ID issent to a disk drive coupled to the designated adaptor card.
 20. Thestorage subsystem as described in claim 17, wherein the disk driveconverts the different loop ID to a unique address for each drive andcontroller within available Arbitrated Loop Port Addresses.